Physiologic And Metabolic Effects

Burkitt and Trowell (2) were the first to report the physiological importance of dietary fiber consumption. Based on epidemiological studies, they showed associations between low-fiber diets and chronic disorders such as constipation, diverticulosis, colon cancer, diabetes, and cardiovascular disease. Since the 1970s research has been carried out that, for the most part, confirms the role of dietary fiber in disease prevention. Normal laxation is an important health benefit of dietary fiber consumption. Certain varieties of dietary fiber have been shown to increase stool weight and frequency, soften feces, increase fecal bulk, and reduce gastrointestinal transit times. This is particularly true of insoluble dietary fibers such as cellulose, found in large quantities in wheat bran, and of soluble but nonfer-mentable fibers such as psyllium gum. Constipation may be prevented, or successfully treated, by increasing dietary fiber intake. Various hypotheses have been suggested as to how dietary fiber affects the composition of fecal material and the frequency of defecation. A likely explanation is the sponge theory. Dietary fiber in the gastrointestinal tract acts as a "water-laden sponge" (3). The sponge entraps or adsorbs water, ions, and nutrients, altering intestinal contents and changing the rate of peristalsis. The presence of fiber also affects the microfloral activity of the colon, the end result being decreased intestinal transit time with increased fecal bulk and water. Stools tend to be softer and larger accompanied by increased frequency of defecation.

Consumption of soluble dietary fibers has been shown to lower blood cholesterol levels in both laboratory animals and humans. Fibers such as oat bran, guar gum, and pectin all have a hypocholesterolemic effect. Several mechanisms of action appear to be responsible for this physiological response. Soluble fibers increase the viscosity of intestinal contents, which alters the mixing and diffusion of nutrients in the intestine and changes rates of nutrient absorption. Impaired bile acid and/or cholesterol absorption from the intestine is thought to lead to lowered blood cholesterol levels. In the colon, most soluble fibers are degraded by the microflora and produce short chain fatty acids (SCFA). It has been hypothesized that SCFA absorbed from the colon may directly inhibit cholesterol synthesis in the liver. High-fiber diets also alter the structure of the intestine. In experimental animals, intestinal length is increased and there is a marked increase in mucosal and muscle mass following fiber consumption (4). It is assumed that morphological changes in the intestine alter absorption patterns thus influencing metabolic processes in the body.

Many varieties of soluble fibers influence the rate of carbohydrate digestion and absorption. It has been shown that when certain fibers are added to test meals, postprandial glucose and insulin levels are decreased (5). In addition, intake of high-fiber foods tends to modulate glucose excursions following meal consumption. This helps to maintain glucose homeostasis and is of particular importance to individuals with impaired glucose tolerance or diabetes.

Prevention of cancer is also considered a health benefit of high-fiber diets. Epidemiological studies indicate that dietary fiber, and in particular a diet rich in cereals and vegetables, helps to prevent colon cancer (6). It is thought that the insoluble fibers that promote laxation and decrease intestinal transit times are responsible for this effect. If toxins and mutagens in foods are moved rapidly through the intestine, exposure of the mucosa to these harmful materials is minimized. Although it is thought that dietary fiber may have a role in preventing numerous cancers including mammary and prostate, this hypothesis has yet to be proven.

5 Ways To Get Rid Of The Baby Fat

5 Ways To Get Rid Of The Baby Fat

Many women who have recently given birth are always interested in attempting to lose some of that extra weight that traditionally accompanies having a baby. What many of these women do not entirely realize is the fact that breast-feeding can not only help provide the baby with essential vitamins and nutrients, but can also help in the weight-loss process.

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